U.S. Pat. No. 4,103,939, dated Aug. 1, 1978 and entitled "Multi Passage Flexible Connector", discloses and claims a multi-channel flexible connector for connecting multiple parallel conduits. The input pipes are connected to a housing and the output pipes are connected to a nipple assembly that protrudes from the housing and is free to move angularly with respect thereto, the connector also being provided with a seat and an elastomeric body for accommodating the angular movements. The nipple is provided with a plurality of passages arranged in a circular fashion about the longitudinal axis of the connector. A corresponding plurality of passages is also provided in the elastomeric body, in the seat and in the housing. The inner and outer surfaces of a flared end of the nipple, as well as a plurality of spherical reinforcing rings within the elastomeric body, have their respective surfaces spherical with respect to a center of deflection located on the longitudinal axis of the housing. The elastomeric body is adhered to the opposing spherical surfaces on the nipple and the seat, and it consequently seals the respective passageways from each other and from the external environment at the interface between the nipple and the seat, while permitting the required angular movement. In order to effect a seal at the interface between the seat and the housing that will accommodate a limited longitudinal movement, the portion of the seat in the vicinity of each of the passageways is formed as an individual piston-shaped member and a corresponding cylindrical recess is provided in the housing with the required seal being maintained between each piston and its corresponding cylinder by means of a plurality of O-rings.
It will be appreciated that, when the pressure inside a particular bore of such a prior art connector exceeds the pressure of the external environment, then a force will be exerted on the face of the respective piston displaced from the coupling's longitudinal axis by an amount equal to the radial distance of the particular bore from the axis. This force will in turn be transmitted by the solid seat element to the elastomeric body and will have the beneficial effect of compressing the elastomeric body and thus promoting the sealing action thereof between the nipple and the seat. The magnitude of the force exerted on a particular one of the pistons is equal to the pressure differential between the interior of the corresponding passageway and the external environment times the effective cross-sectional area of the piston. Accordingly, provided that the pressure in each of the individual passageways is maintained at a fixed nominal value, then by appropriate selection of the cross-sectional area of each of the pistons, the various forces may be equalized such that there will be no resultant net torque exerted upon the seat element which could have the deleterious effect of tending to cause the individual piston portions to be tilted out of alignment and to bind in their respective cylindrical bores. This would interfere with the required compression of the elastomeric body and, especially as the elastomeric is subjected to continued shearing displacements, would thus result in a degradation of the fluid-tight seal and the eventual failure of the coupling.
U.S. Pat. No. 4,076,284, dated Feb. 28, 1978 and entitled "Ocean Floor Riser Connection" discloses and claims a flexible connector suitable for use to effect a flexible connection in the riser between a deep-sea oil well and an offshore floating platform. As noted in that patent, in such an environment a connector is subject to widely varying forces and may involve subjecting the riser connector to production pressures which could be substantially higher than the hydrostatic head on the outer periphery of the connector. The particular connectors disclosed in that patent have but a single passageway surrounded by an elastomeric sealing member which is maintained under compression by a combination of hydrostatic pressures outside of the unit as well as by the high pressures of the operating fluid within the passageway and by tension forces exerted on the connection, with O-rings being used to effect a fluid-tight joint between a collar located at the upper end of the elastomeric seal relative to an internal cylindrical surface of the housing.
U.S. Pat. No. 3,680,895, dated Aug. 1, 1972 and entitled "Flexible Joint Means", discloses and claims an omnidirectionally flexible joint for fluid conduits subject to high pressures and axial loads, including one embodiment having two inner housings that are capable of separate and independent flexing movements with respect to a common outer housing, whereby a given joint deflection can be accomplished by means of simultaneous deflection of both inner housings so that the load on each respective seal assembly may be cut to half of that which would otherwise have been required with the attendant advantages of lower operating stress on each of the seal assemblies and a longer service life.
However, offshore oil drilling and producing operations and, in particular, work-over operations frequently require the use of several contiguous riser passageways which must be sealed from one another and which will be subjected to greatly varying pressures. It will be apparent that the known prior art flexible connectors cannot readily be adapted for use in connecting the individual riser passageways to the wellhead manifold located on the bottom of the sea floor under such circumstances. Accordingly, it was the prior art practice to utilize rigid connections between the several riser passageways and the corresponding outlets on the manifold of the wellhead, and in the event that on account of heavy seas or other extreme conditions, excessive lateral forces would be exerted on the riser passageways required for the workover operation, then the riser passageways would be disconnected from the manifold and the riser pipes raised to the surface until the heavy seas had subsided.
Furthermore, it will be appreciated that excessive compressive forces on the elastomeric seal of a flexible connector are undesirable and that the compressive force preferably should be a function of the highest actual pressure then present in any of the bores, irrespective of the pressure in the other passages. Finally, because of the varying requirements associated with different applications of multi-bore flexible couplings, it is preferable to have a coupling whose components are modular and easily modified to accommodate various sizes, numbers and spacings of passageways, while still maintaining the required relatively uniform distribution of compressive forces on the elastomeric body functioning as the flexible sealing element and the desired relatively compact external configuration.
Accordingly, it is an overall objective of the present invention to provide an improved flexible connector having multiple passageways and an elastomeric seal for accommodating angular movement between the input conduits and the output conduits in which the compressive forces exerted on the elastomeric seal are distributed uniformly with respect to the connector's longitudinal axis.
It is another overall objective of the present invention to provide a flexible connector that will provide a plurality of passageways that will remain sealed from one another and from the external environment under adverse operating conditions during which the connector is subjected to repeated angular movements and the respective pressures inside the individual bores are subjected to wide variations with respect both to the external environment and to one another.
It is still another overall objective to provide a flexible coupling in which the elastomeric body that maintains the seal between the adjacent passageways is subjected to a variable compressive force determined by the greatest pressure in any of the bores.
It is an objective of at least one specific embodiment of the present invention to provide a coupling in which the angular displacement is divided equally between two sets of elastomeric bodies, so as to have the various forces resulting from the angular deflection of the coupling.
Yet another objective is to provide a flexible connector with individual modular components which may be easily changed or modified to accompany various sizes, numbers and spacings of passageways.